Measurement of the semileptonic charge asymmetry in B0 meson mixing with the D0 detector

Collaboration, D0 and Bertram, Iain and Borissov, Guennadi and Ross, Anthony and Williams, Mark and Fox, Harald and Ratoff, Peter and Price, Darren (2012) Measurement of the semileptonic charge asymmetry in B0 meson mixing with the D0 detector. Physical Review D, 86 (7): 072009. ISSN 1550-7998

Abstract

We present a measurement of the semileptonic mixing asymmetry for B0 mesons, a^d_{sl}, using two independent decay channels: B0 -> mu+D-X, with D- -> K+pi-pi-; and B0 -> mu+D*-X, with D*- -> antiD0 pi-, antiD0 -> K+pi- (and charge conjugate processes). We use a data sample corresponding to 10.4 fb^{-1} of ppbar collisions at sqrt(s) = 1.96 TeV, collected with the D0 experiment at the Fermilab Tevatron collider. We extract the charge asymmetries in these two channels as a function of the visible proper decay length (VPDL) of the B0 meson, correct for detector-related asymmetries using data-driven methods, and account for dilution from charge-symmetric processes using Monte Carlo simulation. The final measurement combines four signal VPDL regions for each channel, yielding a^d_{sl} = [0.68 \pm 0.45 \text{(stat.)} \pm 0.14 \text{(syst.)}]%. This is the single most precise measurement of this parameter, with uncertainties smaller than the current world average of B factory measurements.